The Surprising Reasons Floods and Other Disasters Are Deadlier at Night
The darkness itself presents another issue. People tend to look outside for proof that weather warnings match up with their reality, but at night, they often can’t find the confirmation they’re looking for until it’s too late. Some drive their cars into floodwaters, unable to see how deep it is, and get swept away. It’s also harder to evacuate — and try to rescue people — when you can barely see anything. “I invite anybody to just go walk around the woods with a flashlight off, and you find out how difficult it can be,” Ashley said. “Imagine trying to navigate floodwaters or trying to find shelter while you’re in rushing water at night with no flashlight. It’s a nightmare.”
The logic applies to most hazards, but the night problem appears the worst with sudden-onset disasters like tornadoes and earthquakes — and the early-morning flash floods in Texas, where the Guadalupe rose 26 feet in 45 minutes. A warmer atmosphere can hold more moisture, meaning that storms can dump more water more suddenly than they used to.
“We have essentially, because of climate change, put the atmosphere on steroids,” Strader said. It’s on his to-do list to study whether other disasters, like hurricanes and wildfires, are deadlier at night.
When Hurricane Harvey pummeled Texas with rain for days in 2017, people described waking up to water creeping into their homes; the Texas National Guard navigated rescue boats through neighborhoods in the dark, searching for survivors. In recent years, hurricanes have rapidly intensified before making landfall, fueled by warmer ocean waters. That shrinks the window in which forecasters can warn people a strong storm is coming. To compound the problem, at the end of July, the Pentagon plans to stop sharing the government satellite microwave data that helps forecasters track hurricanes overnight, leaving the country vulnerable to what’s called a “sunrise surprise.”
In the past, nighttime conditions have proved useful for slowing wildfires: Temperatures are cooler and the air has more moisture, reducing the likelihood of fires spreading quickly. But climate change is lessening these beneficial effects. The overall intensity of nighttime fires rose 7 percent worldwide between 2003 and 2020, according to a study in the journal Nature. That means fires are increasingly spreading late at night and early in the morning. It was an ultra-dry January night when the Eaton Fire began tearing through Altadena in Los Angeles County. Some residents were woken up in the predawn hours to smoke already in their homes, strangers pounding on their windows, or sheriff’s deputies and rescue volunteers driving by with loudspeakers.
While daytime tornado deaths have declined over time, nighttime fatalities are on the rise, Strader and Ashley have found in their research. (It’s still unclear as to how climate change affects tornadoes.) They found that tornadoes that touch down at night are statistically more likely to hit someone, simply because there are more potential targets scattered across the landscape. During the day, people are often concentrated in cities and sturdy office buildings versus homes, which may be manufactured and not as structurally resilient to floods or high winds.
Night adds dimensions of danger to many types of disasters, but the darkness isn’t the only factor at play — and it doesn’t have to be as deadly, Ashley said, stressing the importance of getting a weather radio and making a plan in case the worst happens. “Have multiple ways to get information, and your odds of survival are extremely high, even in the most horrific tornado situation.”
Kate Yoder is a Senior Staff Writer at Grist. This story was originally published by Grist. You can subscribe to its weekly newsletter here.
